NSSS3.1

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3.1 Volcanoes and Plate Tectonics

Vocabulary

Volcano: A weak spot in the crust where molten material, or magma, comes to the surface.
Magma: A molten mixture of rock - forming substances, gases, and water from the mantle.
Lava: Magma that reaches the surface, it is called lava.
Ring of Fire: The many volcanoes that rim the Pacific Ocean.
Island Arc: The resulting volcanoes create a string of islands called an island arc.
Hot Spot: An area where magma from deep within the mantle melts through the crust like a blow torch.

Outline


What is a Volcano

  • Volcanic activity is a constructive force instead of a destructive force because when lava, magma on the surface, cools down it adds new rock

Location of Volcanoes

  • On land, there are over 600 volcanoes which are active
  • In the sea, there are many more active volcanoes
  • Along the boundaries of the Earth's plates, volcanic belts are formed
  • The most famous one is the Ring of Fire, a volcanic belt which is around the Pacific Plate
  • Many volcanoes occur divergent boundaries or subduction zones

Volcanoes at Diverging Plate Boundaries

  • At the mid-ocean ridge, many volcanoes form
  • In a few places, volcanoes which occur there rise to the surface

Volcanoes at Converging Boundaries

  • Many volcanoes occur on islands, near where an ocean-ocean plate collision happened
  • When these volcanoes happen in a string, they create an island arc

Hot Spot Volcanoes

  • In the middle of continental and oceanic plates, "hot spots'' are there
  • Gradually hot spot volcanoes form a chain of volcanic mountains
    • Ex. the Hawaiian Islands